The S&P had last reached a new closing high on Jan. 26, then retreated more than 10 percent, a correction that lasted until Feb. 8. Friday's new closing high confirmed that the index's bull run remained intact.

Speaking at a research symposium in Jackson Hole, Wyoming, Powell said the Fed's gradual interest rate hikes were the best way to protect the economic recovery, maintain strong job growth and keep inflation under control. His comments did little to change market expectations of a rate hike in September and perhaps again in December.

Investors said they were reassured that Powell's comments stayed in line with previous commentary from the Fed regarding policy. Economic data also boosted sentiment.

New orders for key U.S.-made capital goods increased more than expected in July and shipments growth held firm, the Commerce Department said.

"That's what the markets wanted to hear," said Oliver Pursche, chief market strategist at Bruderman Asset Management in New York. "The economic data and strong environment as a whole is the basis, and (Powell) didn't get in the way."

The Dow Jones Industrial Average rose 133.37 points, or 0.52 percent, to 25,790.35, the S&P 500 gained 17.71 points, or 0.62 percent, to 2,874.69 and the Nasdaq Composite added 67.52 points, or 0.86 percent, to 7,945.98.

For the week, the Dow added 0.47 percent, the S&P gained 0.87 percent, and the Nasdaq increased 1.66 percent.

The small-cap Russell 2000 index also advanced 0.5 percent to reach a new closing high.

A dip in the dollar after Powell's comments helped lift materials and energy stocks as the prices of oil and metals rose. The S&P 500 materials sector jumped 1.2 percent, the biggest percentage gain among the 11 major S&P sectors.

Netflix Inc shares rose 5.8 percent to add the most gains to the S&P 500 after SunTrust Robinson Humphrey upgraded its rating on the stock to "buy" and projected that third-quarter subscriber growth would match or beat Wall Street estimates.

Advancing issues outnumbered declining ones on the NYSE by a 2.50-to-1 ratio; on Nasdaq, a 1.76-to-1 ratio favored advancers.

The S&P 500 posted 36 new 52-week highs and four new lows; the Nasdaq Composite recorded 150 new highs and 31 new lows.

Volume on U.S. exchanges was 5.43 billion shares, compared to the 6.28 billion average over the last 20 trading days. (Reporting by April Joyner; additional reporting by Shreyashi Sanyal and Savio D'Souza in Bengaluru; editing by Nick Zieminski and David Gregorio)